Template-free fabrication of hierarchical graphitic carbon nitride via self-assembled aggregates for enhanced photocatalytic hydrogen evolution activity under visible light

Structure and shape engineering has great potential to enable graphitic carbon nitride (CN) unique nanostructures with adjustable electronic properties and enhanced photocatalytic activities. In this study, a novel type of self-assembled melamine aggregates was formed in dimethyl sulfoxide (DMSO) without additional chemicals and templates, and these aggregates were then directly calcined to obtain three-dimensional hierarchically nanoporous CN. This structure-retention from precursor to CN demonstrated that the structure and shape of CN were free from collapse during melamine thermal polycondensation and thus made vast active sites exposed. Besides, the oxygen dopant resulted from structure-retention adjusted the electronic properties of CN derived from melamine aggregates (MACN), facilitating hydrogen evolution reaction. The Pt-decorated MACN showed the fastest hydrogen production rate of 8.2 µmol·h-1 for 3 wt% Pt/MACN under visible light, which is 4.5 times higher than that of Pt-decorated CN sample obtained from the calcination of commercial melamine precursor. The structure-retention strategy via melamine self-assembly is a facile, rapid, and robust method to access the unique nanostructured CN with enhanced photocatalytic performance under visible light, thereby enriching the toolbox for the fabrication of CN materials.